Make sure you do not have anything in your .xinitrc file that conflicts with the GNOME 2.0 Desktop. If you are not
sure, rename your ~/.xinitrc file to /.xinitrc.orig and try to login again.

Make sure your LD_LIBRARY_PATH does not point to a directory
which contains incompatible versions of the GNOME libraries. The GNOME 2.0
Desktop does not require LD_LIBRARY_PATH to be set at all. If
you must define this for other applications, try adding /usr/lib and /usr/sfw to the beginning of your LD_LIBRARY_PATH.